1. Field of the Invention
This invention relates to a process for the production of dichlorine monoxide. More particularly, the invention is concerned with a process for recovering dichlorine monoxide from hypochlorous acid solutions.
Dichlorine monoxide, Cl.sub.2 O, has been found to be an effective reagent for the bleaching of wood pulp and textiles. Dichlorine monoxide has been made in the laboratory by the reaction of chlorine with mercury oxide, HgO. On an industrial or commercial scale, dichlorine monoxide has been prepared by reacting chlorine with sodium carbonate (soda ash) or sodium bicarbonate in the presence of controlled amounts of water. An example of this approach is found in U.S. Pat. No. 3,914,397, issued Oct. 21, 1975 to W. A. Mueller. In this process, dry gaseous chlorine in the presence of a moist dilutant gas such as air oxygen or nitrogen is reacted with alkali metal carbonates or bicarbonates in the form of dry solids having reactive open structure forms and specified surfaces areas. The process is carried out at a temperature in the range of -20.degree. C. to +30.degree. C. while maintaining the pH at 9.5 or higher.
Gaseous dichlorine monoxide has also been prepared by treating concentrated solutions of hypochlorous acid with anhydrous calcium nitrate. In U.S. Reissue Pat. No. 31,348, issued Aug. 16, 1983 to J. A. Wojtowicz et al, gaseous chlorine is passed rapidly across the surface of an agitated aqueous solution of sodium hydroxide at a reduced temperature. A gaseous mixture of hypochlorous acid, chlorine monoxide and unreacted chlorine is produced which, if dried over anhydrous calcium nitrate, produces dichlorine monoxide.
A slow current of air was passed through a dilute solution of hypochlorous acid (0.2715 N, 1.4% by wt.), through calcium nitrate to absorb water vapor, and through sodium hydroxide to absorb dichlorine monoxide in a study on the ionization of hypochlorous acid by W. A. Noyes and T. A. Wilson (J. Amer. Chem. Soc. 44, 1630-1637, 1922). Moles of dichlorine monoxide in the range of 0.0025 to 0.0114 were collected.
These methods produce mixtures of dichlorine monoxide and chlorine. However the presence of chlorine is undesirable in many applications of dichlorine monoxide.
Further, these methods have not produced dichlorine monoxide in high concentrations and volumes which could economically be used in commercial applications.
Thus there is a need for a process for producing gaseous dichlorine monoxide substantially free of chlorine. In addition, there is a need for a process for producing efficiently in amounts and concentrations for commercial applications.